Background and aim
Sowing canola in mid-April has become standard practice in the far north of the Western Australian cropping zone. The benefits of early sowing were highlighted in a similar variety by time of sowing trial conducted at Binnu in 2015. In that trial TOS 1 (14 April) yielded 1647kg/ha compared to 997kg/ha for TOS 2 (29 April). Hence delaying sowing by 15 days led to 650kg/ha less yield – 43kg/ha/day. While there was some variation between the varieties in the amount of yield loss from the later sowing time this was not significantly different. The results indicated that using the best variety for the area rather than switching varieties based on season length was the best approach. This trial design was repeated in 2016 because growers were asking if further yield improvements could be obtained by sowing even earlier than mid-April.
The aims were to obtain data on late March and early April sowing of canola varieties and determine if changing variety to better match season length improves yield.
The trial was conducted at Department of Agriculture and Food, Western Australia's (DAFWA) Wongan Hills research facility using a plot seeder, plots were 18m long by 1.54m wide. Rainfall at the site exceeded the long term average for Wongan Hills of 388mm. 215.4mm of rain was received from January to 31 March, prior to the first sowing time. Regular rain was received throughout the growing period and conditions were mild over the seed maturation period.
- Six varieties; all were Round-up Ready hybrid plant types and included a range of season lengths. Pioneer 43Y23 (early), Hyola 404RR (early-mid), GT50 (mid), Hyola 525RT (mid-late), Hyola 600RR (late), Hyola 725RT (very late).
- Two times of sowing (TOS) (31 March and 15 April)
Plant density achieved at both times of sowing and all varieties were around the recommended 20-40 plants/m2. Plant density was lower from TOS 1 (27 plants/m2) compared to TOS 2 (37 plants/m2). Hyola 404RR established more plants than other varieties (40 compared to a site average of 32 plants/m2).
When measured on 7 September dry matter production was significantly greater (P <0.05) from the first time of sowing. The variation between varieties was almost significant (P <0.06). GT50 had the greatest biomass and Hyola 525RT the least.
Plants of all varieties were larger from TOS 1 compared to TOS 2. Average plant weight from TOS 1 was almost double TOS 2 and statistically significant (P <0.001). The plant weight of varieties differed (P <0.05) although this did not correlate to season length; the longer season varieties were not always the largest plants.
Yield and seed quality
The average yield of the trial was 2755kg/ha. Averaged across all varieties canola sown on 31 March yielded 2853kg/ha compared to 2658kg/ha for canola sown on 15 April. Hence delaying sowing by 15 days led to 195kg/ha less yield, which is equivalent to an average loss of 13kg/ha/day. There was a variety response; the longest season variety, Hyola 725RT was lower yielding than all other varieties while GT50 was higher yielding than all other varieties. The effect of sowing time by variety was almost statistically significant (P=0.066) and differences in the response to TOS were associated with variety maturity length. The early varieties Pioneer 43Y23 and Hyola 404RR did not have a yield improvement from sowing earlier than mid-April. Hyola 600RR and Hyola 725RT yields decreased by around 260kg/ha from delayed sowing (17kg/ha/day) or 9% and 10%, respectively. GT50 and Hyola 525RT yields decreased by 360kg/ha (24kg/ha/day) or 11% and 12 %, respectively.
For both seed weight and oil content there were differences between varieties (P <0.001) with 43Y23 and GT50 producing lower oil and Hyola 404RR and Hyola 525RT producing larger seed than other varieties, however sowing date did not have a consistent effect.
All treatments had positive gross margin, as expected given the yields but there was a large range from $1306-798/ha. The highest gross margins were obtained from sowing mid and mid-late maturity varieties at TOS 1. Total seed costs were calculated using cost per kilo and the seeding rate, which was adjusted for seed size and germination percentage, consequently seed costs varied significantly from $54-124/ha. Seed rates could have been dropped back at TOS 2 as the plant density achieved was quite high, which would increase gross margins of TOS 2 treatments. Also for Hyola 404RR the large seed resulted in a better field establishment percentage and higher plant density so seed rates of this variety could have been reduced slightly.
|Variety||TOS||Seed cost/kg||Seed rate (kg/ha)||Total seed cost||Total cost||Income||GM|
In general mid-season five and six series mid and mid/late varieties responded best to March sowing while shorter season three and four series varieties produced similar yields from both times of sowing. The seven series variety Hyola 725RT responded to March sowing, but its yields were still not competitive with other varieties. These results match well with NVT data which indicate that the longer season varieties yield better relative to shorter season varieties at high yield potential sites. These often correlate to longer season length sites.
Thanks to Stephanie Boyce, Shari Dougal and DAFWA RSU staff for trial management and measurements. This trial (16GE12) was funded by Department of Agriculture and Food, Western Australia and Grains Research and Development Corporation (DAW00227).